From the Mountaintop to the Tap

Dug many wells recently? Got blisters on your hands from carrying all those pails of water from the stream?

In Southern California, chances are your fresh, clean water is never farther away than the nearest drinking fountain, kitchen tap or garden hose. But have you ever wondered exactly where that water comes from?

The Los Angeles Department of Water and Power--whose job it is to worry about these things--is ready to answer your curiosity with a one-hour tour of its Aqueduct Filtration Plant.

Located at the northern end of the San Fernando Valley--between Granada Hills and Sylmar--the plant is an easily accessible and highly educational resource. The facility--built five years ago at a cost of $146 million--is open to the public, and tours will appeal to water professionals and lay persons alike.

(Apart from school groups, the most frequent visitors are utilities officials and engineers from around the world.)

Unabashedly billing itself as “the most technologically advanced water-treatment facility in the United States,” the plant produces as many as 600 million gallons of fresh water every day. This single-handedly accounts for 75% of the city’s water, with the rest coming from deep wells and through purchases from the Metropolitan Water District.

Thus, as the tour guides like to boast, it is the only water-treatment plant the city has, or needs.

The facility stands at the receiving end of the 338-mile-long series of channels, pipes and tunnels known as the Los Angeles Aqueduct. From high up in the Sierra Nevada down through the Owens Valley and Mono Basin, water travels southward, propelled by gravity through the Mojave Desert and up over Tejon Pass.

Freeway travelers might spot the waterway on the east side of Interstate 5 on the way up to Valencia. There, what looks like a giant escalator flooded with water is actually the home stretch of the aqueduct, as it heads downhill toward the filtration plant.

The tour begins just inside the front doors. Diagrams and charts provide background on the plant and explain the elements of water treatment. Heading upstairs, visitors take in the nerve center of the operation, where engineers keep track of the plant’s functions through a network of computers. This on-line system is so comprehensive that, during off-hours, the entire plant can be managed by two people. If that sounds risky, don’t worry. Every system, including the computer, is backed up by a second, identical system that is prepared to take over in the event of a malfunction.

And speaking of the M word, the complex is constructed of steel-reinforced concrete, strong enough to operate during a 7.4-magnitude earthquake. While upstairs, you also pass by the in-house research laboratory where experimental water-treatment methods are developed and tested.

From here you head outside to a walkway where you can take in the entire operation and learn about what sets this plant apart from others.

While most facilities use chlorine, which can leave behind unwanted chemical substances, to purify water, this one uses ozone gas. That’s right, ozone. You might know it as something that’s disappearing over the North and South poles.

However, in the world of water treatment, ozone is a powerful and quick-acting disinfecting agent that improves the taste, odor and color of water. And when it’s finished reacting with impurities, it leaves behind only oxygen.

A significant portion of the filtration plant is devoted to making ozone. The process is deceptively simple: Air is drawn in from outside, its oxygen content is purified, and then stimulated with electricity. From the walkway, you can see what look like two small concrete bunkers in the near distance. It is here that the process begins.

Stepping inside a second building, you see the other end of the process--four metallic monoliths that are the largest ozone generators in the world.

Proceeding downstairs, you pass one of four contact basins, huge tanks in which ozone is mixed with air and injected into water. Small portholes allow you to watch the gas bubbling up, disinfecting the water and converting into oxygen.

Still downstairs, you’ll notice how the complex’s underground tunnels slope gradually downward. Having dropped as much as 8,000 feet in its long trip south from the mountains, the water will descend another 12 feet during treatment.

By allowing gravity to do all the work, the facility gets away with using very few pumps. Passing beneath a series of flocculation pools, where more particles and impurities are removed, you head back up toward daylight.

By now all that fresh water might be making you thirsty. Not to worry. Your tour guide will invite you to sample the plant’s sparkling cold output from a drinking fountain on the way out.

The final leg of the tour brings you back outside to the filtration beds, an open area that looks like a concrete playground with two dozen small swimming pools.

No diving boards here, though--at the bottom of these pools are 6-foot-thick filters of anthracite coal. As the still-murky water passes through, the last of the impurities are left behind.

If you’re lucky, you’ll be in time to see one of the beds being “backwashed,” as clean water is forced back up through the filter beds, removing the gathered sediment from the coal.

Here’s where the plant really shows off its dedication to recycling and conservation: The water used to clean the beds is directed to a series of reclamation ponds, then pumped back into the plant.

Tours of the Water Works Tours of the Los Angeles Aqueduct Filtration Plant are available Monday through Saturday. For reservations, call (818) 367-5907. Tours are not recommended for children under 12.

Other Department of Water and Power facilities--including pumping stations, hydroelectric plants and other power generating sites--can be toured by special arrangement. For information, call (213) 481-6414.

And let’s not forget waste-water treatment. The Department of Public Works, Bureau of Sanitation, offers a tour of the Hyperion Treatment Plant, the largest on the West Coast. Tours are offered at 9 a.m. and 1 p.m. on Tuesdays and Thursdays. The two-hour tour includes a slide presentation and a tram ride to points of interest. For reservations, call (310) 648-5217.